This relates to ink jets which project droplets outwardly from the orifice of a jet toward a printing medium.
Ink jets typically operate by expelling ink from a chamber of specific volume located within or associated with the jet and contracting the volume so as to expell or project a droplet of ink from the ink orifice. In order for an ink jet to operate properly, it is necessary for the jet to be filled with ink such that contraction of the chamber of specific volume does result in the projection of a droplet of ink from the orifice. Filling the chamber with ink is characteristically referred to as the priming function.
A purging function in an ink jet system may be provided so as to clear an ink jet orifice of debris such as dried ink or dust. The purging function resembles the priming function except that greater quantities of ink may be expelled from the orifice for greater periods of time.
A variety of pumping systems have been proposed and used for an ink jet system to provide the priming and/or purging function. One pumping system is disclosed in co-pending application Ser. No. 203,584, filed Nov. 3, 1980 now U.S. Pat. No. 4,359,744 which provides for a peristaltic pumping action utilizing flexible tubing which couples the ink supply or reservoir to the ink jet. As disclosed therein, the tubing is carried by and associated with a disposable reservoir which is carried by a traveling printing head while the pump drive mechanism is mounted in a stationary position. A rather elaborate mechanism is provided for initiating peristaltic pumping action including solenoids which bring the pump drive mechanism into pumping contact with the flexible tubing. Although some of the pump mechanism is carried by the reservoir, the electromechanical portion of the pump is mounted in the stationary position and not carried on the print head or the reservoir. It will also be appreciated that circuitry must be provided which can generate one type of signal for controlling the ink jet and another type of signal for controlling the solenoids.
A variety of other pumps have been proposed for use in conjunction with priming and purging an ink jet. However these pumps are not well suited for mounting on a movable printing head let alone a disposable reservoir such as that disclosed in the aforesaid copending application.
Copending application Ser. No. 078,131, filed Sept. 24, 1979 now U.S. Pat. No. 4,241,357 discloses an ink jet system employing an electrode adjacent the orifice of an ink for the sensing the presence of ink so as to indicate the prime condition. This is accomplished by utilizing an electrode having an orifice therein which is capable of closing circuit so as to deactivate the priming pump driver.
Copending application Ser. No. 203,582, filed Nov. 3, 1980 discloses an ink catcher adjacent the orifice of an ink jet including a sliding cover.